1. Field of the Invention
The present invention relates to a seat belt retractor, and in particular to a seat belt retractor in which the retracting force of a webbing is reduced when the webbing is extended across the upper torso and the pelvic regions of an occupant.
2. Description of the Prior Art
Conventionally, it has been desirous to reduce the force of webbing on an occupant. One of such devices is disclosed in Japanese Utility model Laid-open Print No. 1-73447 which was published on May 17, 1989 without examination. In this device, a pair of spiral springs are connected, via a ratchet mechanism, to a spool on which a webbing is wound. Though the spool is rotated continuously by the spiral springs in the direction of the retraction of the webbing, when the webbing is extracted the ratchet mechanism is operated to isolate one of the spiral springs. Thus, the retracting force applied to the webbing is reduced.
Moreover, the foregoing construction requires a complex arrangement located near the spool and an enlargement of the device in the axial direction of the spool.